Keiton has been paralysed from the waist down by the leukaemia

Keiton Knight, seven, from Hove in East Sussex, has a white mother and a black father, so he can only find a match from another mixed race person.

But there are "not enough donors of mixed race background", a charity said.

Keiton's appeal has already been to the Notting Hill Carnival. Four clinics will be held in London in October.

He was just four when he was diagnosed with acute lymphoblastic leukaemia in June 2003.

People need to get their blood tested now to see whether they could be a match Keiton's mother, Paris Knight

His mother Paris, 32, said: "If we don't find a matching donor for Keiton he will die, it's as simple as that.

"The doctors are hesitant about giving a timescale because his condition can change on a daily basis.

"But they don't want the search to find a donor to go on beyond November because of the amount of time he has already spent receiving chemotherapy.

"People need to get their blood tested now to see whether they could be a match."

Keiton's donor must have one black and one white parent and be aged between 18 and 40.

But a spokeswoman for the Anthony Nolan Trust said fewer than 3% of volunteers on its register were Afro-Caribbean.